1. Field of the Invention
The invention relates to a circuit board connecting apparatus for electrically connecting a circuit board and another circuit board.
2. Related Background Art
Hitherto, as a method of connecting a terminal portion of a circuit board and another terminal portion, there is a method by soldering, a method by a connector, or the like. Among them, a connector is generally used as a detachable device. FIG. 3 shows an example of such a connecting method by the connector. FIG. 3 is a cross sectional view showing a state in which a circuit board 500 and a circuit board 501 are connected by a connector 502.
The connector 502 has a construction such that a contact 504 of a sandwiching clip shape which has a spring property and is formed by soldering phosphor bronze with nickel is arranged in a housing 503. A terminal 505 of the contact 504 extending to the outside while penetrating a wall surface of the housing 503 is soldered to a terminal 506 of the circuit board 500 by a solder 507.
On the other hand, a terminal portion 508 of the circuit board 501 is inserted into the contact 504 from the opening port side of the connector 502. The contact 504 has a spring property and sandwiches the circuit board 501, so that the contact 504 elastically comes into pressure contact with the terminal portion 508 of the circuit board 501. The terminal portion 508 of the circuit board 501 and the contact 504 are electrically connected. Consequently, the terminal portion 506 of the circuit board 500 and the terminal portion 508 of the circuit board 501 are electrically connected through the contact 504 of the connector 502.
FIGS. 4A and 4B show cross sectional views of another conventional example. FIG. 4A shows a state before a connector is joined. FIG. 4B shows a state after the connector was joined.
According to a connector 512 of the conventional example shown in FIGS. 4A and 4B, a contact 514 made up of a contact member having a mountain-like cross sectional shape is provided in a housing 513. The housing 513 has a movable portion 518 which is rotatable by a hinge portion H and has a structure such that the contact 514 is depressed downward by rotating the movable portion 518 in the direction shown by an arrow from an opening state.
A terminal portion 515 of the contact 514 is soldered to a terminal 516 of a circuit board 510. A circuit board 511 is inserted into an opening port of the connector 512. After that, the movable portion 518 of the housing 513 of the connector 512 is rotated in the direction shown by the arrow.
When the movable portion 518 is rotated in the arrow direction, the movable portion 518 is fixed and enters a state shown in FIG. 4B.
In the fixed state shown in FIG. 4B, a force is applied to a terminal portion 517 of the circuit board 511 by a spring force of the contact 514, so that the contact 514 and terminal portion 517 are electrically connected.
The terminal portion 516 of the circuit board 510 is, therefore, connected to the terminal portion 517 of the circuit board 511 through the contact 514 of the connector 512.
However, the foregoing conventional method of joining the circuit boards by the connector has the following problems.
Although the contact of the connector is made of a copper alloy material having a good conductivity such as phosphor bronze, titanium copper, chromium copper, or the like having a spring property, it is relatively hard.
The terminal portion of the circuit board is made of copper or copper with a solder of gold, Ni, tin, or the like.
The contact portion has many concave and convex portions when it is seen from a micro precision. However, as a degree of concave and convex portions of the contact portion of the connector is reduced and as a joint area is increased, a connector which enables a larger current to flow can be formed.
It is, therefore, necessary to increase the joint area and to increase a contact pressure. However, in order to raise the contact pressure, not only the spring material but also the plate have to be thickened and the structure has to be enlarged in size. Such a structure is difficult in the conventional connector.
Particularly, in the conventional connector, as the connector has a large number of pins and a narrow pitch, the joint area decreases and the contact pressure also decreases, so that the reliability of the joint deteriorates.
The terminal of the circuit board which is inserted into the connector is positioned and formed while using an external shape as a reference. The terminal portion corresponds to the contact in a one-to-one relational manner. Therefore, when a variation occurs in the external dimensions of the terminal of the circuit board which is inserted into the connector and patterns of the external shape and the circuit board are deviated, a problem such that the terminal portion of the circuit board and the contact of the connector are not matched occurs.
Particularly, the above problem is further remarkable in the connector having a larger number of pins and a narrower pitch. It will be obviously understood that if it is intended to solve those problems, costs rise.